40 AMPHITHERIID&. 
and opercular pieces, is no fissure at all; but, in the two 
specimens of Amphitherium Prevostii of the Oxford Museum, 
and in the larger specimen of Amphitherium at York, which 
exhibit the inner side of the ramus of the jaw, is a distinct 
groove with an entire surface, answering to that which 
exists in the corresponding part of the jaw of the mar- 
supial Myrmecobius and the Wombat. 
The Myrmecobius is an insectivorous Mammal, and also 
marsupial, and it does not possess approximated and 
parallel incisores, but widely separated and diverging ones ; 
they are, indeed, symmetrical with those of the opposite 
ramus, as in other Mammalia, but, as no one has yet seen 
an entire jaw of an Amphitherium or Phascolotheriwn, 
it is hard to understand the meaning of the assertion, that 
their incisores are not symmetrical: they are undoubtedly 
small; but, if they are almost as large as the supposed 
canine, such likewise are their porportions in Myrmecobius, 
and many Jnsectivora. The lower jaw of Amphitherium 
Bucklandi, (Phascolotherium, mihi,) is not more arched than 
in the recent Dasyurus, whose jaw is placed beside the fossil 
in the British Museum ; and it will be plainly seen that 
the condyloid, or articular surface, instead of ‘ passing 
obliquely into the hard imbedding rock,’ stands boldly 
out, and demonstrates a form diametrically opposite to 
that concave one which characterizes the jaws of reptiles 
and fishes. Thus much I have thought it necessary to 
state as to matters of fact, respecting which, however, 
the specimens speak plainly for themselves. 
Not any of the jaws hitherto discovered present eleven 
similar multicuspid molares: even in the fragment of one 
side of the lower jaw figured by M. Prevost, which con- 
tains ten of the series of twelve molares, which is the true 
number in the genus Amphitherium, the fractured state 
